The present invention relates to the sterile preparation of polymers. More specifically, the present invention relates to moderate heat sterilization of polymers, and preferably, heat-labile polymers. The methods of the present invention involve the formation of suspension comprising a water-miscible organic liquid and a polymer, followed by subsequent heat sterilization.
Polymers are used extensively in the preparation of food, medical and pharmaceutical compositions. The type of polymer used will depend on the functional needs of a given composition. For example, if viscosity enhancement is required, polymers providing viscosity enhancing effects, such as polyvinyl alcohol, polyvinyl pyrrolidone, various cellulosic polymers such as carboxymethyl cellulose or hydroxypropylmethyl cellulose, may be used. If a surfactant is required, surfactants such as polaxamines, polaxamers, alkyl ethoxylates or others may be used. If a gelling polymer is required, polymers such as gellan, carageenan or carbomers may be used.
Certain preparations of food, medical or pharmaceutical compositions require the employment of sterilization methods in order to eliminate microbial contamination. Various methods of polymer sterilization have been available in the art. For example, techniques of filter sterilization can be used. Such methods usually involve the filtration of the composition, partial formulation or individual ingredients of the compositions, wherein such components are passed through a filter with a pore size too small for microbes to pass through. Autoclaving, another method of sterilization, involves the steam heat and pressure treatment of a composition, or individual components of the composition, for a given time to effect the elimination of microbes. Other methods of sterilization involve the irradiation of the composition, or individual components, with particle/energy rays such as gamma rays or electron beams. Still other methods of sterilization involve the dry heat treatment of the polymers.
Although the foregoing methods of sterilization are useful for numerous polymers, certain polymers require more complicated steps of sterilization. For example, if certain composition or components are too viscous or comprise polymers or particles that are too large to pass through the pores of a filter, then filter sterilization will not be useful. If certain compositions or individual components are hydrolytically unstable, then autoclaving methods will not be effective. Although dry heat sterilization techniques may provide an alternative to polymers susceptible to autoclaving hydrolysis, there are still some polymers which degredate or otherwise lose cross-linking ability during dry heat treatments. Additionally, some compositions may comprise components that present a variety of sterilization problems which make the sterile preparation of such compositions possible, using conventional techniques, but labor and cost prohibitive. Therefore, what is needed are new methods of sterilization which provide effective sterilization of polymers, and especially, difficult to sterilize polymers, thereby providing a labor/cost improvement over the prior art methods.